Ambulatory robotic systems may generally be categorized into one of two classes. The first of these classes includes ambulatory robotic systems that are statically stable. The second class includes ambulatory robotic systems that are dynamically stable. Statically stable ambulatory robot systems are stable when unpowered, whereas dynamically stabilized ambulatory robotic systems include active, powered mechanisms to stabilize the system. In this regard, statically stable ambulatory robots generally have a lower center of gravity with a larger footprint in order to passively maintain stability without the intervention of active sensors or actuators. Dynamically stabilized ambulatory robots generally include control structures and actuators that actively maintain the stability of the ambulatory robot. As such, dynamically stabilized ambulatory robots can have a smaller footprint because these robots are dynamically stabilized by the robot “balancing.” This balancing may include the control of actuators in response to a sensed position or change in position to maintain stability.
Dynamically stabilized ambulatory robot platforms have been used in applications to produce an entertaining or whimsical effect. Such effects result from the dynamically stabilized ambulatory robot remaining stable when the system appears, from the perspective of a casual observer, as though the system should not remain stable. For instance, Segway™ devices are dynamically stabilized two wheeled ambulatory robotic systems that use gyroscopes and other mechanisms to dynamically maintain the stability of the system. Such devices may also provide for propulsion of an ambulatory robotic system along a plane or surface. These systems have been used successfully in the past to stabilize and propel robotic systems for utilitarian as well as entertainment purposes. However, due to limitations of these systems, the utilitarian as well as entertaining applications of these systems are limited.
For instance, as the understanding of the technology behind these types of dynamically balanced systems has become more widespread, the understanding of these systems by the general public has increased such that the entertainment value and/or whimsical nature of these types of platforms lessens due to people being aware of and understanding the principles governing such systems.
Additionally, some of these two wheeled dynamically stabilized ambulatory robotic systems are non-holonomic, and thus the range of motion is limited for these systems. Holonomic, in the field of robotics, refers to a system's ability to independently control all degrees of freedom of the system. For instance, an ambulatory robot designed to move about a surface or plane may generally exhibit at least three degrees of freedom. These may correspond to translation in both axes of the plane as well as rotation in a direction generally perpendicular to the plane. In order to be holonomic, the robot must be able to fully move in any one of these degrees of freedom independently of any other degree of freedom. For example, the ambulatory robotic system must be able to move in any direction along the plane without rotating in a direction perpendicular to the plane (e.g., move side to side and front to back without first turning or rotating).
As such, non-holonomic ambulatory robotic systems may be limited in the range of motion capable of being produced. This is a particular disadvantage when using these robotic systems for entertainment purposes. For instance, when using these non-holonomic ambulatory robotic systems as platforms for animatronic characters, puppets, operators, props, or the like, the limited range of motion may spoil the illusion that an operator or object is in fact balancing on or controlling the movement of the robotic system.
One system that addresses some of the limitations of two-wheeled dynamically stabilized or statically stabilized ambulatory robotic systems is presented in U.S. Patent Application Publication No. 2008/0024175 by Hollis, which is hereby incorporated by reference in its entirety. This robotic system includes a controller capable of achieving dynamic balancing by way of controlling actuators. The robot includes fiber optic gyroscopes and electromechanical accelerometers to measure the position and dynamics of the dynamic balancing mobile robot. In turn, the controller is operative to control a plurality of actuators in conjunction with a ball upon which the platform is dynamically balanced.
However, the robotic system shown in the '175 publication has several drawbacks and limitations. For instance, the mobile robot device operates by way of a reverse mouse wheel type design. In such a design, the entire system is supported by, and dynamically balanced on, a ball or sphere. The actuators for controlling the ball in order to dynamically balance the system must be positioned precisely at the equator of the sphere to facilitate holonomic control over the supporting ball. In this regard, at least half of the ball is obstructed by the system, thus minimizing the visibility of the ball. Again, when used in an entertainment application, such obstruction of the ball that occurs in the '175 publication reduces the entertaining effect because the mystique associated with the illusion that the ball is controlled by an animatronic character, puppet, or the like is destroyed. That is, the illusion that a character or puppet is controlling the ball is diminished as a large portion of the ball must be covered.
Therefore, the prior art contains no ambulatory robotic system that is capable of holonomic motion along a surface while obscuring a relatively small amount of the sphere or ball upon which the locomotive and balancing forces are applied.